java.lang.StackOverflowError when codec does not have an encode method

[TheVastyDeep]

logstash 7.15.2, installed using yum, run from the command line. The following configuration

input { generator { count => 1 lines => [ '' ] } }
output { udp { port  => 2055 codec => netflow host => "127.1.2.3" } }

results in

warning: thread "[main]>worker0" terminated with exception (report_on_exception is true):
java.lang.StackOverflowError
    at usr.share.logstash.logstash_minus_core.lib.logstash.codecs.base.encode(/usr/share/logstash/logstash-core/lib/logstash/codecs/base.rb:48)
    at usr.share.logstash.logstash_minus_core.lib.logstash.codecs.base.multi_encode(/usr/share/logstash/logstash-core/lib/logstash/codecs/base.rb:64)
    at org.jruby.RubyArray.each(org/jruby/RubyArray.java:1820)
    at usr.share.logstash.logstash_minus_core.lib.logstash.codecs.base.multi_encode(/usr/share/logstash/logstash-core/lib/logstash/codecs/base.rb:64)
    at usr.share.logstash.logstash_minus_core.lib.logstash.codecs.base.encode(/usr/share/logstash/logstash-core/lib/logstash/codecs/base.rb:48)
    at usr.share.logstash.logstash_minus_core.lib.logstash.codecs.base.multi_encode(/usr/share/logstash/logstash-core/lib/logstash/codecs/base.rb:64)
    at org.jruby.RubyArray.each(org/jruby/RubyArray.java:1820)

because in codec/base.rb encode calls multi_encode, which calls encode.

Personally I think the netflow codec should be modified to add an encode method which throws an exception saying "You cannot use this codec on an output".

[kares]

Thanks for the report, indeed the base class assumed the codec to override multi_encode or encode.

Personally I think the netflow codec should be modified to add an encode method which throws an exception saying "You cannot use this codec on an output".

Yes, this would be the best approach, (e.g. a different codec not supporting decode raises).

It might be better to have the issue report at https://github.com/logstash-plugins/logstash-codec-netflow/issues so someone looking at the codec is aware of it.

[TheVastyDeep]

I have opened 196 against the netflow codec, so if the override is a requirement of the base filter this can be closed.

[kares]

yes due how codecs are handling either to re-def encode or multi_encode the base.rb isn't going to change anytime soon.